In a business system including a storage device, such as a disk array device, using an HDD (Hard Disk Device) as a storage medium, concentration of accesses to a certain region on the storage device in a certain time zone may decrease the performance of the entire system.
For example, when a plurality of client devices included in the business system read system information for activation in a time zone of a start of business, accesses to a region on the storage device which stores the system information are concentrated.
As a method for avoiding such a decrease in performance due to accesses to a certain region, the following methods are known.
(1) An HDD (Hard Disk Drive) is added to a storage device for load dispersion.
(2) Data is rearranged on a storage medium (an SSD (Solid State Drive), a higher-speed HDD, and the like) capable of realizing higher-speed access.
(3) A capacity of a cache memory used for a primary cache using a RAM (Random Access Memory) or the like is increased to enhance cache hit rate.
(4) A cache memory used for a secondary cache using an SSD, a FlashROM (Read Only Memory), or the like is introduced to enhance cache hit rate.
In the method where a cache memory is added as described above in (3) and (4), when a large access load is applied to a storage device, the cache memory operates to reduce an access load applied to a region having become the cause. Therefore, depending on an operation status, a cache memory may have been already used in a certain time zone where a decrease in performance needs to be avoided, since the cache memory caches data of a region other than a region which is the cause of the decrease in performance in the certain time zone. In this case, the added cache memory is not effectively used.
Japanese Laid-open Patent Publication No. 2009-157749, for example, discloses a method for effectively using a cache memory for such accesses to a certain region in a certain time zone.
The storage system disclosed in Japanese Laid-open Patent Publication No. 2009-157749 sets priority related to the use of a cache memory for each of a plurality of pieces of data for every time zone and determines a piece of data for which a cache memory is used in each time zone based on the set priority.
As a related technology, Japanese Laid-open Patent Publication No. 2003-337721 discloses a technique for changing a storage configuration in accordance with a storage configuration change schedule predetermined by an administrator.